It has been difficult in the prior art to miniaturize dynamic position responsive compasses, and the like, which depend upon a pendulum for establishing the horizontal plane of the earth's surface in the presence of dynamic movements of the instrument. The pendulum itself is a limiting factor in the miniaturization because of critical shape, mass, friction, etc. that relate to instrument accuracy and response time when dynamically moving under such conditions as when being towed in rough water behind a vessel.
In magnetic detection instruments, miniaturization itself is otherwise advantageous in that larger size bodies surrounding a magnetic detector provide more possibilities of stray magnetic field patterns that produce noise and limit accuracy. Thus, smaller size eliminates some sources of magnetic noise disturbances that can reduce sensitivity or accuracy, which may be found in surrounding electronic circuit wiring, any movable conductive materials and certain types of materials including some classes of ceramics that react magnetically.
Instrument accuracy and sensitivity is critical, such as for response of electronic magnetic compass systems to very subtle changes in the earth's magnetic fields caused by geological structures or to motion of a streamer cable in rough seas. Dynamically operable magnetic field detectors are essential to precisely measure the local magnetic field, and need to respond quickly, particularly when used in air or sea vessel surveys. One limiting response time deterrent is the necessity to use a pendulum, which may be large enough to have considerable inertia and thus may limit the dynamic response time under quickly changing positions encountered for example in rough seas, etc. Also pendulum movement can cause magnetic noises in various ways.
In any instrument involving a gimbal assembly, there are potential gimbal-related inaccuracies because of friction, inertia, mechanical misalignments, bearing wear, shifting of masses under dynamic conditions, etc. These introduce special problems that are critical to instrument accuracy.
The housing environment of such instruments is also critical, and can introduce dynamic shock-induced inaccuracies as well as magnetic field disturbances and reliability in use under various environmental conditions, such as sea water. The distribution of mass and weight of the instrumentation is also critical in this respect.
One significant problem has been establishing electrical communications or wiring to eliminate noise disturbances and to handle very low level signals under the dynamic signal and environmental working conditions that are encountered. This is particularly difficult to resolve wherever movable parts are involved because of stray currents, impedance changes in contact points with wear, magnetic fields, and different positional performance.
Accordingly, in the prior art there has not been satisfactory reliable and accurate level-seeking magnetic field sensing instrumentation, particularly in miniature, and especially for use in magnetic compass systems. It is therefore the primary object of this invention to provide improved instrumentation for overcoming the various aforesaid defects of the prior art.